Among the many applications of ionic liquids (ILs) is their potential use as battery electrolytes. Ethylammonium nitrate (EAN) is a protic ionic liquid and was the first IL to be discovered. Interest in this IL has increased considerably in recent years due to its various potential applications in the fields of chemistry, electrochemistry and biology. The possible use of EAN in electronic devices is of particular interest, owing to its high electrical conductivity, good electrochemical window (even at room temperature) and high thermal stability. Although EAN could be used directly as an electrolyte, its application can be optimized by mixing the IL with a metal salt. So far, most studies have focused on the use of lithium, but its scarcity and high toxicity have led to the search for alternatives, one of which is aluminium. In addition to the thermophysical properties of ILs that make them suitable for the use for which they are being investigated, the environmental toxicity of ILs must also be investigated. Although they have been considered to cause little harm because they are non-volatile, several studies have shown that they can have toxic effects on the terrestrial environment.

In this study, the impact on basal soil respiration of EAN alone and of EAN combined with aluminium salt was investigated in order to assess whether the metal salt increases the potential toxic effects of EAN in soil. For comparative purposes, the impact of the aluminium salt on soil respiration was also studied. Two soils with similar pH and texture but with different organic matter contents were used, as it has been shown that organic matter can buffer the toxicity of both organic and inorganic pollutants. The aluminium salt did not affect soil respiration in either soil. However, the EAN-aluminium salt combination strongly affected respiration in the soil with low organic matter content, while in the soil with high organic matter content only a small reduction in the total amount of C-CO₂ emitted and a slight modification in the kinetics of respiration were observed, relative to the soil exposed to EAN.